The manufacture of microfabricated devices, such as integrated circuits, microprocessors, microfluidic components, among many others, can require very high levels of precision in all aspects of the fabrication process, in order to accurately and reliably produce the assorted microscale features of these devices. Many non-microscale devices similarly must be efficiently manufactured in order to achieve cost effectiveness.
The fabrication of many devices, whether microscale or non-microscale, often entails the bonding or laminating of two or more substrate layers, in order to produce the assembled device. While many bonding techniques are routinely utilized to mate or laminate multiple substrates together, these methods all suffer from a number of deficiencies. For example, silica-based substrates are often bonded together using thermal bonding techniques. However, in these thermal bonding methods, substrate yields are often less than ideal, as a result of uneven mating or inadequate contact between the substrate layers prior to the thermal bonding process. Similarly, in bonding semi-malleable substrates, these bond voids or variations in the contact between substrate layers, e.g., resulting from uneven application of pressure to the substrates, may adversely impact device performance. In particular, when a bond void coincides with, or otherwise adjoins, a microchannel or other desired cavity of a microfluidic device, it alters or interferes with fluid flow patterns within the device, which can bias assay results. Additionally, optimal semiconductor device function typically requires the interface between the semiconductor and heat sink to be free of unattached regions between semiconducting layers in order to properly minimize electrical resistance heating and to maximize the conduction of heat away from the layers. Further, the presence of voids in bonding between laminated optical surfaces also leads to the diminished utility of assorted ocular instrumentation. Many other manufacturing methods are also negatively impacted by the occurrence of bond voids.
Particular sources of bond voids in, e.g., microfluidic devices, include particles trapped between substrates during the bonding process. There are generally two types of particles that cause incomplete bonding in microfluidic devices. The first type includes glass, polymer, or other substrate fragments, e.g., that are generated as by-products during the fabrication of features, such as microchannels into the substrate surfaces. These “hard defects” remain throughout the fabrication process and act as spacers between substrate layers to create the unattached regions. The other type of particle is organic matter that typically decomposes during certain high temperature bonding techniques. Nonetheless, these organic materials or “soft defects” typically leave behind voids in the bond between substrate surfaces.
Many applications performed using various electronic, microfluidic, or other devices entail precise temperature control over selected device regions. For example, high-throughput is achieved in certain microfluidic assays such as the polymerase chain reaction (PCR) step in, e.g., single nucleotide polymorphism (SNP) genotyping, by performing multiple reactions simultaneously in parallel reaction channels of a given device. This typically requires temperature uniformity across the multiple channels. In many devices, however, significant amounts of heat are lost, e.g., to the surrounding substrate material. Heat lost in this manner generally results in unequal temperature distributions among channels, which thereby inhibits reaction specificity.
Accordingly, due to the cost of substrate materials, and the precise manufacturing requirements of many microscale and non-microscale devices generally, and microfluidic devices, particularly, it would be desirable to provide techniques for preventing bond voids from affecting functionalized or otherwise specified regions of bonded surfaces. It would also be desirable to selectively regulate temperature within many of these devices. The present invention provides these, and other features, which will become apparent upon complete review of the following.